(a) Field of the Invention
The present invention relates to an apparatus for controlling generation of electric power in a vehicle, and more particularly, to an apparatus and a method of controlling generation of electric power in a vehicle that is capable of calculating a target state of charge (SOC) of a battery on the basis of a SOC of the battery and an amount of accumulated current according to individual driving modes and performing a feedback control on generation of an alternator to follow the target SOC, thereby maintaining an optimal SOC and improving fuel efficiency.
(b) Description of the Related Art
Vehicle makers throughout the world have used various technologies for improving fuel efficiency in order to overcome high oil prices. Examples of the technologies for improving fuel efficiency include a system for controlling generation of electric power.
The system for controlling generation of electric power allows an engine control unit to read information for the current, voltage, and temperature of a battery from various sensors mounted on electrodes of the battery, determines a target generating voltage according to driving modes of a vehicle, such as an acceleration mode, a deceleration mode, a constant-speed mode, and an idle mode, on the basis of the read information, and controls driving of an alternator to control the generation of electric power.
The system for controlling generation of electric power charges and stores regenerative energy generated during the deceleration mode in the battery, and uses the energy charged in the battery in the acceleration mode, the constant-speed mode, and the idle mode to decrease the generation of the alternator, thereby minimizing fuel consumption.
In a general vehicle, even when the SOC of the battery is normal, the alternator supplies to the battery, not only the current consumed in the vehicle but also a surplus current of several amperes to prevent the battery from being discharged. The system for controlling generation of electric power controls the amount of the surplus current, which is supplied to prevent the battery from being discharged, to be approximately zero, thereby decreasing the unnecessary generation of the alternator.
The vehicle uses the system for controlling generation of electric power to achieve not only the above-described objects but also various objects.
According to a technology that is disclosed in Korean Patent laid-open Publication No. 2004-0078430, in the case where, when an engine is in an idle mode, as the result of monitoring a battery voltage, the battery voltage decreases for a predetermined time at a predetermined voltage or less, a control operation is formed such that RPM of the engine is maintained to be adaptable for a current state of the battery regardless of current consumers.
Accordingly, according to this technology, it is possible to prevent exhaust gas and noise from being excessively generated and the battery from being overdischarged due to the overload in an idle mode, which results in preventing starting-off of the vehicle from occurring in advance.
According to a technology that is disclosed in Korean Patent laid-open Publication No. 2003-0005408, allowable power supplied to current consumers is determined oil the basis of generation allowed in a generating unit and a discharge allowed in a charging unit, and power consumption of an air conditioning unit is calculated to increase power supplied to the air conditioning unit within a range of the allowable power, thereby controlling the generation of the generating unit in the range of allowable generation.
Accordingly, according to this technology, it is possible to prevent traveling of the vehicle from being affected due to the power consumption by the air conditioning unit.
According to a technology that is disclosed in Japanese Patent Laid-open Publication No. 06-113599, a generation stop control operation is performed for a predetermined time only in the case where driving information of the engine is maintained in a predetermined normal range, thereby preventing the battery from being excessively discharged.
According to a technology that is disclosed in Japanese Patent Laid-open Publication No. 14-272012, a state of a battery is measured through a current sensor that is disposed on a power line of the battery to determine a generating target voltage, thereby performing a generation control operation, and in the case where a voltage of the battery detected during the generation control process is within an abnormal determination range, it is determined that a charging system is abnormal.
A generation control logic of a generation control system, which is currently used in the vehicle for the purpose of improving fuel efficiency, is divided into a bulk mode, an absorption mode, and a float mode according to the SOC of the battery.
In the bulk mode, all generation control operations are prohibited and the SOC is maintained. In the absorption mode and the float mode, according to each of driving modes, such as an acceleration mode, a deceleration mode, a constant-speed mode, and an idle state, a target voltage is separately set, and a generation control operation is performed.
However, according to the above-described generation control logic of the related art that is applied in the vehicle, it is very difficult to save fuel consumption because of a structural problem.
For example, even though the driving state is in a deceleration mode, a time required to control the charged energy and the target voltage should be changed according to the SOC of the battery. However, in the current generation control logic, since the function is not applied flexibly, it is not possible to achieve an effect of saving fuel consumption.
Further, a surplus current, which is supplied to the battery to prevent discharging, needs to be controlled to become zero for various current consumers and driving modes. However, in the generation control logic in accordance with the related art, since this control function is not applied flexibly, it is difficult to control the surplus current to become zero.
Further, since charging efficiency is changed according to the temperature of a battery electrolyte solution and the charged amount is changed according to the SOC of the battery, the generation control prohibition period after the starting-on should be changed according to each state. However, because the current generation control logic operates as a time constant, it is not possible to actively and stably perform the generation control according to each state of the battery.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.